1. Field of the Invention
This invention relates to an apparatus for automatically connecting and routing wire elements between two or more terminals on a base or workpiece.
2. Prior Art
It is common practice in automatic wiring apparatus to feed double strands of wires from a feed unit for bonding to a first and a second bond point on a card. Each bond point has ground and signal pads to which each of the wires is bonded. Prior to bonding, the insulations from the wires are stripped; a bonding unit then engages the wires and bonds said wires to the ground and signal pads, respectively.
After bonding the wires to the first bond point, the exact distance between the first and second bond point is determined. Wire lengths, equivalent to this distance are fed from wire spools and a wire twisting assembly twists said wires. The card is then positioned so that the second bonding point is within reach of the bonding unit. The stripping process is again performed and the wires are bonded to the second point. The wires are then broken off adjacent to the second bond point, thus completing a net.
Although the prior art wiring systems are satisfactory for their intended purposes, these systems are not suitable for high speed operation. As a result, a relatively long period of time is required to complete a net, i.e., bond a pair of wires to a first bond point on a workpiece and route the twisted wire to a second bond point. In short, these prior art wiring systems are relatively slow. The slowness of these systems stems from the fact that the bonding process is divided into two steps, namely, stripping the insulation from the wires and then bonding the strip wires to the workpiece. The problem of slowness is further aggravated by the fact that the wires have to be twisted before routing to the second bonding point. Due to the slowness of these prior art wiring systems, there has been a significant increase in production cost.
Another significant disadvantage of the above wiring systems is that it can only wire relatively short nets. As a result of this deficiency, the system is effectively a point-to-point system, i.e., the length of a net (distance between the first and the second wiring point) is relatively short. In fact, the length of a net is in a direct line from the first to the second bond point. The restriction in the length of a net, stems from the fact that the feed tube wherein the wires are twisted can accommodate only a fixed length of twisted wires and if the distance between the bonding points exceed this fixed length, the system is useless. To meet this net restriction, after bonding the wires to a first bond point, the distance to the second bond point is determined and the wire is twisted prior to positioning the card for bonding at the second bond point. However, it is well known to technicians in the wiring art that in some wiring applications, e.g., wiring a second level package (i.e., a package containing a plurality of cards) relatively long nets are required, and to meet this need, the prior art wiring systems are inadequate.
Another disadvantage of the prior art wiring systems is that after bonding the wires to a first bond point, the system cannot route twisted wires, through channels and around guide posts affixed to a second level package or workpiece, to the second bond point. As is well known in the wiring art, a second level package contains a multiplicity of wires. In order to maintain these wires in an orderly fashion, channels and guide posts are affixed to the second level workpiece to maintain these wires in, respective, geometrical patterns. It is therefore necessary to have a wiring system which is capable of wiring and routing the wires on such second level workpiece. However, in spite of efforts to improve the routing capabilities of the prior art wiring systems, the problem has not been solved.
Finally, the prior art wiring systems generally do not orientate the position of the ground and signal wire so as to obtain alignment with the ground and signal pads on a workpiece. It is not uncommon in the wiring art to find that the orientation between the ground and signal pads on a workpiece at a first bond site is different from the orientation at a second bond site, i.e., at a first bond point the signal pad is to the right of the ground pad while at a second bond point the signal wires is to the left of the ground pad. In order to maintain proper alignment between the ground wire and the ground pad, and the signal wire and the signal pad, the orientation of the wires must be changed. The prior art wiring systems generally do not change the orientation of the ground and signal wires and therefore, this creates an undue restriction in preparing the signal and ground pads on a workpiece to be used with the prior art wiring systems.